MUSCLE CONTRACTION

Question 1

What structure is an action potential propagated along via?

Answer 1

Transverse t tubules

Question 2

Explain the journey of an action potential through a muscle

Answer 2

• AP generated at motor end plate
• AP propagated along inside of muscle via transverse t tubules
• Goes deep inside muscles fibres and to separate myofibrils

Question 3

What is contraction triggered by?

Answer 3

The intracellular release of Ca2+

Question 4

How is Ca2+ released in muscle cells?

Answer 4

• After depolarisation, the inside of cells is positive
• AP activates a DHP receptor
• This stimulates the release of Ca2+ from the sarcoplasmic reticulum

Question 5

What is the fate of ACh?

Answer 5

Reuptake of choline into the presynaptic terminal or enzymatic breakdown

Question 6

What is Myasthenia Gravis?

Answer 6

• Muscle weakness during sustained activity
• Autoimmune disease of nicotinic acetylcholine receptors
• This means there are less receptors at the NMJ
• AP not generated because EPP not generated

Question 7

What is the treatment for myasthenia gravis?

Answer 7

• Drugs that inhibit ACh enzymes
• ACh remains bound to receptors for longer increasing potential and likelihood of EPP
• This increases likelihood of AP